Sterilizing Seeds

What are some ways to sterilize the outside of large seeds like Astrophytums, so that they don't get covered later in the white fuzz? Anyone have experience with hydrogen peroxide, or bleach? What concentrations are good?
Thanks,
IX

I collect Astrophytum seeds by myself and wash seeds well by water and dried.
I used seedrising pottingmix, organic base in market and so I use a systemic fungicide.

1. Spray over the fungicide on top of pottingmix in a pot before sowing seeds.
2. Sowing seeds
3. Spray over the fungicide on top of pottingmix and seeds again just after sown seeds.

You should not use the fungicide when germination was started.
The name of fungicide is "Fongarid".

I have never seen white fuzz in my seedling pots.

Thank you Hana, Only had this happen once, but it killed 95% of the astros that germinated.

Just a bit of an update on this post. I've gotten the Fongarid, and have just started using it.
Now out of that batch of 300 seeds that did get hit hard by the fungus, I grafted the remaining 13, out of which 6 still rotted anyhow, leaving 7 survivors from the original 300.